JPH03294519A - Sheath-core conjugate fiber - Google Patents

Abstract

PURPOSE:To obtain the title fiber suitable for tire useful for tires of trucks and buses, having excellent mechanical characteristics, by blending specific amounts of a core component prepared by mixing specific two components with a sheath component. CONSTITUTION:(A) 30-90wt.% blend component of two component polymers of (i) 90-30wt.% polyester consisting essentially of polyethylene terephthalate unit and having >=0.6 intrinsic viscosity (eta) and (ii) a polyethylene-2,6-naphthalate consisting essentially of ethylenenaphthalene-2,6-dicarboxylate and having >=0.6 (eta) intrinsic viscosity, as a core component is blended with (B) 70-10wt.% polyamide having >=2.8 relative viscosity (etar) of sulfuric acid as a sheath component to give the objective yarn having >=6.0g/d strength, <=20% elongation, >=60g/d initial tensile strength resistance degree and <=7% dry heat shrinkage percentage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to high-strength, high-modulus fibers suitable for industrial material applications, particularly for rubber reinforcing materials.

More specifically, it has excellent mechanical properties such as high strength, high modulus, and improved dimensional stability, and has excellent adhesion with rubber, heat resistance in rubber, and is a cause of deterioration in the durability of core-sheath composite fibers. It is an object of the present invention to provide a core-sheath composite fiber suitable for rubber reinforcement, which has improved interface peeling between a core component and a sheath component.

[Prior art] Polyethylene-2,6-naphthalate (hereinafter referred to as 2.6-PE
Fibers consisting of N) have high strength, high modulus, and high heat resistance in rubber, and are being used as rubber reinforcing materials for various industrial materials, especially tire cords, power transmission belts, and conveyor belts. be.

Many attempts have been made to improve the adhesion to rubber, which is a drawback of fibers such as polyethylene terephthalate and polyethylene naphthalate.One of these efforts has recently been to coat the surface layer of polyester with polyamide.
Composite fibers with appropriate physical properties are disclosed in JP-A-1-9721.
It is described in Publication No. 1. JP-A-1-97211 describes a composite fiber having a polyester core and a nylon 66 sheath, the degree of polymerization of each component polymer and the proportion of the core polymer being specified.

[Problems to be Solved by the Invention] Although the core-sheath type composite fiber described in JP-A-1-97211 has considerably improved adhesion and durability,
In some applications, for example, tires used under harsh conditions such as tires for passenger cars running at high speeds, it is not sufficient.
Additionally, improved dimensional stability, heat resistance and ride comfort are required.

Further, in the above-mentioned Japanese Patent Application Laid-open No. 1-97211, the polyamide component of the sheath provides improved adhesion to rubber, and the polyester component of the core attempts to maintain modulus and dimensional stability. Although adhesion is certainly sufficiently improved by this method, modulus, dimensional stability, and heat resistance are the same properties that polyester fibers generally have, and are not improved in any way.

In addition, since polymers such as polyester and 2.6-PEN have poor compatibility with polyamide polymers such as nylon 6 and nylon 66, fibers with a core-sheath composite structure produced by normal spinning methods are It was easy to peel and break and did not have sufficient durability for practical use. Especially the stretching process,
The problem is that the core-sheath interface is destroyed by the tire cord processing processes such as twisting and dipping, the tire vulcanization process, and the repeated stretching and compression fatigue experienced during tire running, making it impossible to obtain the performance expected of the original core-sheath composite fiber. .

The 2.6-PEN fiber described above has poor adhesion to rubber, and especially when repeatedly exposed to a high temperature atmosphere for a long time, the adhesion to rubber decreases significantly. In particular, when used as a tire cord, the heat generated when the car is running accumulates inside the tire, resulting in high temperatures that can cause the tire to lose its adhesive strength with the rubber and peel off.Also, the tire cord becomes fatigued due to the repeated compression and stretching that the tire undergoes. The problem was that the tire would break and the tire would burst as a result.

The object of the present invention is to overcome the problems in the prior art as described above, thereby achieving excellent adhesion to rubber, significantly improved dimensional stability, high modulus, and heat resistance in rubber compared to conventional composite fibers. The object of the present invention is to provide a core-sheath composite fiber suitable for rubber reinforcement, which has fatigue resistance, and in particular has sufficient durability against peeling of the polymer at the core-sheath composite interface, which has not been achieved with conventional techniques.

[Means and effects for solving the problem] The structure of the present invention is as follows: (1) In the core-sheath composite fiber, the ratio of the core component is 30 to 9.
A core-sheath composite fiber comprising 0% by weight and a sheath component ratio of 70 to 10% by weight, the sheath component being polyamide,
The core component is a polyester whose main component is essentially polyethylene terephthalate units, and ethylene naphthalene-2.
, 6-dicarboxylate as a main component and polyethylene-2,6-naphthalate, and the blending ratio of polyester in the core component is 90 to 30% by weight. core-sheath composite fiber.

(2) In the core-sheath composite fiber described in (1) above,
The intrinsic viscosity of the polyester that is one of the core components [
η] is 0.6 or more, the other component of the core component, polyethylene-2,6 naphthalate, has an intrinsic viscosity [η] of 0.6 or more, and the polyamide sheath component has a sulfuric acid relative viscosity ηr of 2.
A core-sheath composite fiber characterized in that the fiber is 8 or more.

(3) In the core-sheath composite fiber described in (1) and (2) above, the composite fiber has a strength of 6.0276 or more, an elongation of 20% or less, and an initial tensile resistance of 60 g /
The core-sheath composite fiber has a dry heat shrinkage rate of 7% or less.

The core component of the core-sheath composite fiber according to the present invention is a blend component of polyester and 2,6PEN. When the blend ratio of polyester is 90% by weight or more, the effect of improving modulus and dimensional stability is recognized, but it does not reach the point where there is a significant difference. If the blending ratio of polyester is less than 30% by weight, the fatigue resistance will be lowered, and this is substantially undesirable as an industrial fiber for use in rubber reinforcement.

Polyester in the core-sheath composite fiber according to the present invention; 2.
The ratio of the core component consisting of a blend of 6-PEN is 30 to 9.
It is 0% by weight. If the blended core component of polyester and 2.6-PEN is less than 30% by weight, the dimensional stability, modulus and heat resistance of polyester and 2.6-PEN cannot be effectively utilized. In addition, the core component consisting of a blend of polyester and 2.6-PEN is 90% by weight.
If the content exceeds this amount, the flexibility of the composite fiber will be lost and the fatigue resistance will be reduced.

The core-sheath composite fiber according to the present invention is a fiber mainly used in the field of industrial materials, and strength is one of the many required performances as an industrial fiber. High strength is required if other performance requirements are satisfied.

In the core-sheath composite fiber according to the present invention, the polyester and 2.6-PEN used as the core component have an intrinsic viscosity [η] of 0.6 or more, and the polyamide sheath component has a sulfuric acid relative viscosity ηr of 2.6-PEN.
By setting it to 8 or more, the core-sheath composite fiber has high strength and high heat resistance, and is suitable for industrial use, especially as a rubber reinforcing fiber.

The core-sheath composite fiber according to the present invention has a 2.6
- The blend ratio of PEN polymer and the ratio of polyamide and the properties of the core-sheath composite fiber obtained using these polymers have a high strength of 6,0276 or more and an initial tensile resistance of 60 g/d or more, The elongation is 20% or less, and the dry heat shrinkage rate is 7.0% or less. More preferable composite fiber properties are a strength of 7,0276 or more and an initial tensile resistance of 70 g/d.
By satisfying elongation of 8 to 16% and dry heat shrinkage of 6.0% or less, significantly improved dimensional stability, high modulus, heat resistance, and It can be used as a fiber for industrial purposes, especially for rubber reinforcement, with excellent fatigue resistance and peeling durability of the polymer at the core/sheath composite interface.

The polyester constituting one of the core components of the core-sheath composite fiber according to the present invention is a polyester having an intrinsic viscosity [η] of 0.6 or more, preferably 0.7 or more and consisting essentially of polyethylene talphthalate units. The copolymer component may be contained to an extent that does not substantially reduce the physical and chemical properties of the polyethylene terephthalate polymer, for example, less than 10% by weight. Copolymerization components include dicarboxylic acids such as isophthalic acid and naphthalene dicarboxylic acid, alcohol components such as propylene glycol and butylene glycol, and ethylene oxide.

2) 6-PEN, which is the other component of the core component of the core-sheath composite fiber according to the present invention, is substantially ethylene-naphthalene-2,6-PEN having an intrinsic viscosity [η] of 0.6 or more, preferably 0.7 or more.
The main component is dicarboxylate, and if necessary 2.6
- The copolymer component may be contained to an extent that does not substantially reduce the physical and chemical properties of PEN, for example, less than 10%.

As copolymerization components, dicarboxylic acids such as isophthalic acid and diphenyl dicarboxylic acid, diol components such as ethylene oxide, propylene glycol, butylene glycol, and other components are used.

On the other hand, the polyamides used as the sheath component of the core-sheath composite fiber according to the present invention include polycabramide, polyhexamethylene adipamide, polytetramethylene adipamide, polyhexamethylene dodecamide, polyhexamethylene dodecamide, and polyhexamethylene dodecamide. These include xamethylene terephthalamide, polyhexamethylene isophthalamide, etc. Among them, polyhexamethylene adipamide-based polymers are preferably used.

In addition, the polyamide may contain, for example, less than 10% of ε-cabramide, tetramethylene adipamide, hexamethylene dodecamide, etc., to the extent that physical properties such as strength are not substantially reduced. Components such as hexamethylene dodecamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide may be copolymerized or blended.

Furthermore, the above-mentioned polyamide may optionally contain thermal oxidative deterioration inhibitors, matting agents, pigments, light stabilizers, etc., which add other properties to the extent that the physical properties such as the strength of the fibers of the present invention are not reduced.
A heat stabilizer, an antioxidant, an antistatic agent, a dyeability improver, an adhesion improver, etc. can be added. In particular, copper salts and other organic and inorganic compounds can be added as thermal oxidative deterioration inhibitors. When used for industrial purposes, in particular, copper salts such as iodized steel, copper acetate, copper chloride, and copper stearate should be used in an amount of 30 to 500 ppm as copper, and alkali metal halides such as potassium iodide, sodium iodide, potassium bromide, etc. 0.0
It is preferable to contain 1 to 0.5% by weight and/or 0.01 to 0.1% by weight of an organic or inorganic phosphorus compound.

The core-sheath composite fiber according to the present invention is produced by a novel method detailed below.

As the polyester which is one of the core components mentioned above, a polyester consisting essentially of polyethylene terephthalate having an intrinsic viscosity [η] of 0.6 or more, usually 0.7 or more is used.

The other component of the core component, 2.6-PEN, has an intrinsic viscosity [
η] 0.6 or more, usually 0.7 or more 2) 6-PEN whose main component is substantially ethylenenaphthalene-2,6-dicarboxylate is used.

As the polyamide polymer of the sheath component, a high polymerization degree polymer having a sulfuric acid relative viscosity of 2.8 or more, usually 3.0 or more is used.

The core component polyester polymer and 2.6-PEN polymer are melted in separate extruders and then blended in a kneading device, or both polymers are blended and then melted. The melting temperature is 290-330°C.

On the other hand, the polyamide polymer of the sheath component is melted in a separate extruder at 280-310°C.

The core component polymer, which is a blend of the molten polyester and 2.6PEN polymer, and the sheath component polymer, which is made of a polyamide polymer, are each introduced into a composite spinning device heated to a temperature of 290 to 310°C, and passed through a composite spinning nozzle. Spun as core-sheath composite fiber.

The spinning speed is set to a high speed of 1000 m/min or more.

Immediately below the composite spinneret, a heating cylinder and a heating cylinder are provided to provide a heated atmosphere of 200° C. or more, preferably 260° C. or more over a distance of 10 cm or more and 1 m or less. The spun core-sheath composite fiber passes through the above-mentioned heated atmosphere, is rapidly cooled and solidified with cold air, is then applied with an oil agent, and is then taken off by a take-off roll that controls the spinning speed. The core-sheath composite fibers taken off are undrawn yarns.

Control of the heating atmosphere directly below the spinneret is important in order to maintain stringiness during high-speed spinning of the present invention.

The taken-off undrawn yarn is drawn continuously without being wound up, or it is drawn in a separate step after being wound up.

The adoption of high-speed spinning improves the dimensional stability and durability of the composite fiber at high temperatures, as well as the peeling durability of the core-sheath interface.

Next, the undrawn yarn is hot-stretched at a temperature of 80° C. or higher, preferably 200° C. or higher, to obtain a drawn yarn.

The stretching is carried out in two or more stages, usually three or more stages, and the stretching ratio is in the range of 1.1 to 7.0.

The drawn yarn thus obtained has the characteristics of the core-sheath composite fiber according to the present invention described above.

Next, explanations will be given based on Examples, and the definitions and measurement methods of the fiber characteristics and cord characteristics described in the main text of the specification and Examples of the present invention are as follows.

Characteristics of polyester core component Intrinsic viscosity [η]: A sample was dissolved in an orthochlorophenol solution and measured at 25°C using an Ostwald viscometer.

2.6-Characteristics of PEN core component Intrinsic viscosity [η]: Dissolve the sample in a mixed solvent of phenol and orthodibenzene (mixing ratio 6:4), and use an Ostwald viscometer to determine the
Measured at °C.

Characteristics of polyamide sheath component Sulfuric acid relative viscosity ηr: 0.25 g of sample was dissolved in 25 cc of 98% sulfuric acid and measured at 25° C. using an Ostwald viscometer.

Characteristics of composite fiber (a) Strength, elongation, and initial modulus: Strength, elongation, and initial modulus were determined according to the definition and measurement method of JIS L1017. The specific conditions for the tensile test to obtain the SS curve are as follows.

Take the sample into a whole shape, leave it in a temperature and humidity controlled room at 20℃ and 65% RH for more than 24 hours, and then
-4L" type tensile testing machine (manufactured by Orientic Co., Ltd.), the measurement was performed at a test speed of 25 am and a tensile speed of 30 cm/min.

(b) Dry heat shrinkage rate: Take a sample in a general shape, leave it in a temperature and humidity controlled room at 20°C and 65% RH for 24 hours or more, then apply a load equivalent to 0.1 g/d of the sample and measure the length. A L sample is processed in an oven at 150°C for 30 minutes under no tension. After the treated sample was air-dried and left in the temperature and humidity control room for 24 hours or more, the load was applied again and the length was measured. It was calculated from the following formula.

Dry heat shrinkage rate = (LL,)/LX100 Characteristics of composite fiber cord (a) Strength, elongation, intermediate elongation: Measured in the same manner as in the case of the fibers. The intermediate elongation is the elongation when the strength is shown as determined by the formula below.

(4,5X D X n )/ (100OX2)K
g However, D: Drawn yarn fineness n: Number of twisted yarns For example, two yarns with a drawn yarn fineness of 1500 denier are combined and twisted: +-do 1500/2 has an intermediate elongation at 6.75 kg.

(b) Dry heat shrinkage rate: Measured in the same manner as for the composite fibers, except that the treatment temperature was 177°C.

(c) GY fatigue life: Compliant with JIS L1017-1.3.2.1A method. However, the bending angle was 90°.

(d) GD fatigue life Compliant with JIS L1017-1.3.2.2. However, the expansion was 6.3% and the compression was 12.6%.

(e) Adhesiveness.

According to JIS 1017-3.3.1A.

(f) Heat-resistant adhesion.

Evaluation was carried out in the same manner as in item (e) above, except that the heat treatment during vulcanization was carried out at 170° C. for 60 minutes.

(G) Heat resistance in rubber: The dip cords arranged on a rubber sheet were sandwiched between separately prepared rubber sheets, and heat-treated under a pressure of 50 kg/cm2 for 3 hours in a press heated to 170°C. The cord strength before and after treatment was measured, and the strength retention rate was determined, which was used as a measure of heat resistance.

[Example] Examples -1 to -3, Comparative Examples -1 to -7 A polyester polymer with an intrinsic viscosity [η] of 0.8 and a 2.6-PEN polymer with an intrinsic viscosity [η] of 0.8 were blended. Polymer, and 0.02% by weight of iodized steel and 0 potassium iodide
．． Each hexamethylene adipamide polymer containing 1% by weight of sulfuric acid and having a relative viscosity ηr of 3.3 was melted in a 40φ xtruder type spinning machine, introduced into a composite spinning pack, and then mixed with polyester in the core through a core-sheath composite spinneret at 2°. A blended polymer of 6-PEN was spun as a composite fiber with hexamethylene adipamide polymer in the sheath part. Core component polyester and 2.
The blending ratio of 6-PEN and the composite ratio of the core component and sheath component are shown in Table 1. The cap used had a hole diameter of 0.4 mmφ and 120 holes. Polymer temperature is polyester and 2.6-PE
Melt the N blend polymer at 305°C and hexamethylene adipamide at 290°C, and set the spinning pack temperature to 2.
It was spun at 95°C. A 30 cm heating cylinder was attached directly below the mouthpiece, and the atmosphere inside the cylinder was heated to 300°C. The atmosphere temperature inside the cylinder is the atmosphere temperature measured at a position 10 cm below the mouth surface and 1 cm away from the outermost thread. An annular chimney with a length of 40 cm is installed under the heating cylinder, and a temperature of 40 m/cm is attached from the circumference of the yarn at 20°C.
The yarn was cooled by blowing cold air perpendicularly to it. After applying an oil agent, the yarn speed was controlled with a take-up roll rotating at the speed shown in Table 1, and then the yarn was continuously stretched without being wound up. Stretching is carried out by 5 pairs of Nelson type rolls.
After stretching in stages, the film was subjected to relaxation heat treatment with 3% relaxation and wound up.

The stretching conditions were as follows: Take-up roll temperature was 60°C, first stretching roll temperature was 120°C, second stretching roll temperature was 190°C, third stretching roll temperature was 220°C, and the tension adjustment roll after stretching was not heated. The one-stage stretching ratio was 70% of the total stretching ratio, and the remainder was divided into two stages for stretching. Silk production was carried out by changing the discharge amount in accordance with the spinning speed and the draw ratio, and the discharge amount was varied in accordance with the spinning speed and the draw ratio so that the fineness of the drawn yarn was about 500 denier.

Three of the obtained drawn yarns were combined into a yarn of 1500 denier.

The spinning conditions, the obtained drawn yarn properties, and the fiber structure parameters were determined using commercially available nylon 66 fiber for tire cords (12
60-204-1781), and polyethylene terephthalate (PET) fiber (1500-288-702C)
These are shown in Table 1.

Using the drawn yarn obtained in the above example, a green cord of 1500/2 was obtained by first twisting and first twisting in opposite directions at a rate of 40 T/10 cm. However, the number of twists of N66 was 39T/10cm, and the raw cord was 1260/2. This raw cord was applied with an adhesive and heat-treated using a dipping machine manufactured by Ritzler to obtain a dip cord.

The dip liquid contained an adhesive component consisting of 20% resorcinol, formalin, and latex, and was adjusted so that 4% of the adhesive component adhered to the cord.

The heat treatment was carried out at 225° C. for 80 seconds without stretching so that the intermediate elongation of the dip cord was about 5%.

Nylon 66 was treated under the same heat treatment conditions and stretched to an intermediate elongation of about 9%.

The PET fibers were subjected to a two-bath adhesion treatment in a conventional manner, heat treated at 2400C for 120 seconds, and stretched to an intermediate elongation of about 5%.

The dip cord thus obtained was evaluated for heat resistance in rubber, adhesiveness, fatigue resistance, etc., and the results are shown in Table 2.

The core-sheath composite fiber dip cord of the present invention has fatigue resistance equal to or higher than conventional polyester dip cord, and is a high-strength dip cord that has significantly improved monylus, dimensional stability, heat resistance in rubber, and heat-resistant adhesive properties. It shows that.

(The following is a blank space) [Effects of the invention] The core-sheath composite fiber of the present invention has significantly improved modulus, dimensional stability, and heat resistance in rubber compared to conventional composite fibers, and has excellent adhesive properties, especially when resistant to high temperature history. The heat-resistant adhesion and fatigue resistance after drying were significantly improved. Therefore, when used as a tire cord, for example, the durability against repeated fatigue during tire running and heat generation during running is extremely good. That is, it can be used as a tire cord for tires of relatively large passenger cars, light trucks, trucks, buses, etc. It is especially suitable as a carcass cord for large radial tires.

Furthermore, since the core-sheath composite fiber of the present invention has the above-mentioned excellent physical properties, it can be useful not only as a rubber reinforcing material other than tire cords, but also for general industrial material applications.

Claims (3)

[Claims] (1) In the core-sheath composite fiber, the ratio of the core component is 30 to 9
A core-sheath composite fiber comprising 0% by weight and a sheath component ratio of 70 to 10% by weight, the sheath component being polyamide,
The core component is a polyester whose main component is essentially polyethylene terephthalate units, and ethylene naphthalene-2.
, 6-dicarboxylate as a main component and polyethylene-2,6-naphthalate, and the blending ratio of polyester in the core component is 90 to 30% by weight. core-sheath composite fiber. (2) In the core-sheath composite fiber described in claim 1, the intrinsic viscosity [η] of the polyester that is one component of the core component is 0.6 or more, and the other component of the core component is Intrinsic viscosity of polyethylene-2,6-naphthalate [η
] is 0.6 or more, and the sulfuric acid relative viscosity ηr of the sheath component polyamide is 2.8 or more. (3) In the core-sheath composite fiber described in claims 1 and 2, the strength of the composite fiber is 6.0 g/
d or more, elongation is 20% or less, initial tensile resistance is 60g
/d or more, and a dry heat shrinkage rate of 7% or less.